This 3-year intervention development study is designed to develop and pilot test a family-school intervention for young children with attention-deficit/hyperactivity disorder (ADHD). The intervention being developed in this study, Family-School Success for Early Elementary school children (FSS-EE), targets young children with ADHD (i.e., those in kindergarten and first grade) at a time in their development when family involvement in education and family-school partnership is critical. This early intervention program applies evidence-based strategies involving family-school collaboration, daily report cards, home-based educational activities, and relationship building between parent and child to improve educational and family functioning. After a 1-year period of intervention development and refinement, the intervention will be pilot tested with 68 children. Children with ADHD (Combined, Inattentive, and Hyperactive- Impulsive Types) in kindergarten and first grade will be randomly assigned to FSS-EE or a non- specific comparison (COMP) treatment. The two groups will be stratified according to medication status, ADHD subtype, gender, and presence of a comorbid learning disability, oppositional defiant disorder, and/or internalizing disorder. Outcomes will be assessed at mid- treatment, post-treatment, and 2-month follow-up across four domains: (a) intervention acceptability, (b) family involvement in education, (c) home behavior and parent-child interaction, and (d) academic performance and school behavior. The effect of treatment will be evaluated using longitudinal, mixed effects models applied to the targeted outcome variables. Also, the magnitude of treatment effects will be determined by computing effect size estimates. Attention-deficit/hyperactivity disorder (ADHD) occurs in an estimated 5% to 10% of the general population of children. ADHD is strongly associated with significant academic and family impairments, and children with this disorder are at high risk for school drop out and serious health problems in adolescence and adulthood. This proposed project targets young children when they begin their formal education (kindergarten and grade 1) to promote family and school success through effective inter-systemic partnerships.